Anthropometric correlates of blood pressure among school children in Nagpur city , central India : A cross-sectional study

Context: On the basis of emerging evidence, it is now apparent that primary hypertension is detectable in the young and that it occurs commonly. The longterm health risks for hypertensive children and adolescents can be substantial. Early diagnosis of hypertension (HT) is an important strategy in its control. Previous studies have documented that hypertension may begin in adolescence, perhaps even in childhood. Aims: To determine the prevalence of hypertension and its correlation with anthropometric variables like height, weight and body mass index (BMI) among school-going children in Nagpur city, Central India. Settings and Design: Cross-sectional study done in one randomly selected school. Materials and Methods: School-going children aged between 12 and 16 years were included in the study. The weight and height were measured using a standard procedure. Blood pressure measurements were taken by a mercury sphygmomanometer. Hypertension was diagnosed if blood pressure was more than 95th percentile for the age and height. The distributions of blood pressure by anthropometric characteristics were studied. Statistical Analysis Used: Mean, standard deviation, correlation coeffi cient and χ2 test were used for statistical analysis. Results: The overall prevalence of hypertension was found to be 11.77%. Blood pressure of both genders appears to have positive correlation with anthropometric characteristics. Conclusions: Increase in anthropometric measurements like height, weight and BMI were found to be positively correlated with hypertension among school children in the present study.


INTRODUCTION
The prevalence of hypertension in children and adolescents seems to be increasing. [1]This rise is partially because of the increasing prevalence of obesity among children and adolescents, as well as a growing awareness of this disease.There is evidence that hypertension in children and adolescents can lead to adult hypertension. [2,3]Presence of hypertension in children and adolescents may contribute to the early development of coronary artery disease.Previous reports have shown that early development of atherosclerosis does exist in children and adolescents and may be associated with childhood hypertension. [4,5]propriate early-stage diagnosis and interventions of hypertension in children and adolescents are important for reducing the risk of hypertension-related disorders in adults.
Keeping in view the seriousness of problem on one hand and lack of data about the prevalence of hypertension among school children in Nagpur on another, the present study was undertaken among the school children in Nagpur, to fi nd out prevalence of hypertension and the relationship of hypertension with anthropometric variables like height, weight and body mass index (BMI).
Gandhi Govt.Medical College, Nagpur, Maharashtra, India.The study population comprised students aged 12 to 16 years living in the study area.Out of 13 schools, one school was selected by simple random sampling method.Students from 8 th to 10 th standard were included in the study.Permission from school authority was sought before the start of the study.Institutional ethical committee's clearance was sought before the start of the study.

Data collection
All students present in the classes at the time of interview were included in the study.In all, 450 students were interviewed.Every student was interviewed personally by an investigator using a selfadministered, pretested questionnaire.
General information regarding age, sex, religion, diet and addiction was collected using a pretested proforma.Anthropometric measurements such as weight was taken by a standardized weighing machine with accuracy up to 0.1 kg while height was measured using a standard stadiometer with accuracy up to 0.5 cm.Blood pressure measurements were taken by a standard mercury sphygmomanometer.Three blood pressure measurements were taken at an interval of 5 minutes and the average of the three readings was used in the analysis.
Hypertension was diagnosed if blood pressure was more than 95 th percentile for the age and height. [6,7]BMI was calculated and classifi ed according to WHO [8] into fi ve categories based on z-scores.The cutoff values of z-score for overweight are BMI >+ 1SD (equivalent to BMI 25 kg/m 2 at 19 years), obesity > +2SD (equivalent to BMI 30 kg/m 2 at 19 years), thinness <−2SD, severe thinness <−3SD and normal within −1SD to +1SD.
The distribution of blood pressure by anthropometric characteristics like height, weight and BMI were studied.

Data analysis
Data were entered in Microsoft Excel 2007 and analyzed with Graphpad Prism 5. Mean and standard deviation were calculated for categorical data and χ 2 test was used as a test of signifi cance.Pearson's Correlation coeffi cient was calculated to assess correlation between hypertension and height, weight and BMI of school children.Mean age (± SD) of the school children was 14.11 ± 1.25 years.Even with the short span of fi ve years in the study (12-16 years)  the mean blood pressure increased signifi cantly with age [r = 0.19 for systolic blood pressure (SBP) and r = 0.07 for diastolic blood pressure (DBP)] as evident from [Table 2].The mean SBP of both sexes was 110.39 mm Hg at the age of 12 years and 116.76 mm Hg at the age of 16 years, an increase of 6.37 mm Hg.Similarly, the increase of DBP was observed as 4.43 mm Hg for the same group.So, the age effect was found to be more for SBP in the present study.

Out
The result revealed that SBP and DBP of both sexes have a positive correlation (P < 0.01) with height; correlation of SBP with height was found to be 0.19 for boys and 0.21 for girls, and that of DBP were 0.21 and 0.26 for boys and girls, respectively [Table 3].In both sexes, a rise is observed in mean SBP and DBP with increase in mean weight [Table 4].In the present study, correlation coeffi cient of SBP with weight was 0.35 and 0.36 and that of DBP was 0.30 and 0.33 in boys and girls, respectively.
In our study, 32 (7.11%) children were overweight and obese and 357 (79.33%) were having normal BMI, while the remaining 61 (13.56%) were underweight [Table 5].Among these 32 children, 18 (56.25%)were hypertensive; of the remaining 418 children, 35 (8.37%) were hypertensive [Table 6].When this association of higher BMI with hypertension was studied, it was found to be statistically signifi cant (P = 0.0000).Also, the result revealed that SBP and DBP of both sexes have a positive correlation (P < 0.01) with BMI; correlation of SBP with BMI was found to be 0.39 for boys and 0.21 for girls, and that of DBP with BMI was 0.20 and 0.32 in boys and girls, respectively.

DISCUSSION
In our study, we found 11.77% prevalence of hypertension among adolescents.Durrani et al. [9] reported 9.4% prevalence of hypertension in the same age group i.e., 12-16 years in Aligarh.Also similar prevalence (11.7%) was reported by Chadha et al. [10] in Delhi.Other studies done in different parts of India reported a vast range in the prevalence of hypertension in children and adolescents showing as high as 21.5% to as low as 3.67%. [11,12]Other researchers across India also found varied prevalence of hypertension among adolescents.Taksande et al. [13] reported 5.75% in rural Wardha, Khan et al. [14] reported 9.78% prevalence in Ahmedabad, Mane et al. [15] found 4% prevalence in Western India.In New Delhi, 7.84% prevalence was reported by Singh et al. [16] Also, Borade et al. [17] reported 10.91% prevalence of hypertension in Pune among adolescents.This varied prevalence may be due to different criteria used for diagnosis of hypertension and varied socio-cultural and socioeconomic environment of the adolescents residing in different parts of India.
We found slightly lower prevalence of hypertension in girls (11.76%) than in boys (11.79%).This difference in prevalence of hypertension was not found to be statistically signifi cant (P > 0.05).Similar results were reported by Prabhjot et al. [18] in Amritsar, Punjab, with 8.3% prevalence of hypertension in boys and 6.52% prevalence in girls.But Durrani et al. [9] found lower prevalence of hypertension in boys (9.36%) than in girls (9.4%).Also, there is varied prevalence of hypertension in different age groups.The difference in patterns of blood pressure between males and females and varied prevalence    of hypertension in different age groups are probably related to certain biological, psychosocial factors and puberty timings. [13] our study, we found the positive correlation between hypertension and the anthropometric variables like height (P < 0.0001), weight (P < 0.0001) and BMI (P < 0.0001).Overall coeffi cient of correlation of height with blood pressure was 0.19 for SBP and 0.24 for DBP.SBP and DBP of both genders established the positive correlation (P < 0.0001) with height, which is in accordance with the fi ndings of Durrani et al, [9] Gupta et al. [19] and Saha et al. [20] The correlation coeffi cient of SBP and DBP of both genders also showed a positive correlation with weight [SBP r = 0.35 (boys) and 0.36 (girls) and DBP r = 0.30 (boys) and 0.33 (girls)], which agreed with the fi nding of Durrai et al. [9] [SBP r = 0.47 (boys) and 0.50 (girls) and DBP r = 0.46 (boys) and 0.42 (girls)] and Gupta et al. [19] [SBP r = 0.55 (boys) and 0.58 (girls) and DBP r = 0.61 (boys) and 0.52 (girls)].
Similarly other studies done in different parts of India also showed a positive correlation of SBP and DBP with height and weight of adolescents.Taksande et al. [13] showed positive correlation of height with SBP (r = 0.39) and with DBP (r = 0.31).They also showed positive correlation between weight of adolescents and SBP (r = 0.39) and with DBP (r = 0.28).Saha et al. [20] also reported signifi cant positive correlation of height [SBP r = 0.62 (boys) and 0.54 (girls) and DBP r = 0.52 (boys and girls)] and weight [SBP r = 0.77 (boys) and 0.76 (girls) and DBP r = 0.76 (boys) and 0.63 (girls)] with SBP and DBP of both genders.
Overall, the mean BMI of the study participants was found to be 18.11 ± 2.68, while mean BMI of boys was 17.38 ± 2.52 and that of girls was 18.87 ± 2.64.Similar results were reported by Kapil et al. [21] who found that mean BMI for boys was 20.76 kg/m 2 and for girls it was 21.02 kg/m 2 .Mane et al. [15] also reported a BMI of 19.11 kg/m 2 for boys and 18.92 kg/m 2 for girls.Rahman et al. [22] also reported a mean BMI of 18.5 ± 4.3 in a study done among school children (mean age 14 ± 1.3 years) in Karachi, Pakistan.These differences in BMI can be attributed to socioeconomic and environmental differences.
In the present study, we found 7.11% overweight and obese adolescents.Prevalence of hypertension among these was 56.25% (18/32) as compared to the prevalence in normal and other children i.e., 8.37% [Table 6].And this difference in the prevalence was found to be statistically signifi cant (P = 0.0000).Raj et al. [23] in 2007 determined the relationship of obesity with blood pressure.
Systolic or diastolic incident hypertension was found in 17.34% of overweight children versus 10.1% of the remaining students.Desai et al. [24] reported 5% prevalence of overweight adolescents in Surat city while Rahman et al. [22] estimated 7% and 2% prevalence of overweight and obesity, respectively, which are similar fi ndings to our study.
It is evident from this school-based epidemiological study that increase in BMI predisposes the adolescent individual to higher blood pressure and subsequently, hypertension.A statistical signifi cance was found between overweight/obesity and hypertension in the present study.A similar fi nding was also reported elsewhere in India; Chakraborty et al. [12] found 17.12% prevalence of overweight and 2.45% prevalence of obesity among adolescents of Kolkata city.They also found the statistically signifi cant association between presence of hypertension and overweight and obesity (P < 0.001).Khan et al. [14] reported 10.44% and 5.77% prevalence of overweight and obesity, respectively in adolescent school boys (12-19 years) in Ahmedabad city.Nanaware et al. [25] showed signifi cantly positive correlation between BMI and SBP (r = 0.81, P < 0.001) and with DBP (r = 0.72, P < 0.01) in the age group of 13-16 years.
Mane et al. [15] also reported that the increasing BMI contributed to increase in SBP (P = 0.000) and DBP (P = 0.000) in their study.Shah et al. [26] reported 8.94% prevalence of obesity and 20.9% prevalence of hypertension among adolescents of Surat city.They also found that the prevalence of hypertension adolescents was more in obese as compared to normal (P = 0.0034).Thus, our fi ndings are consistent with the above studies.

CONCLUSION
Increase in anthropometric measurements like height, weight and BMI were found to be positively correlated with hypertension among school children in the present study.

Recommendation
Children must be screened to detect and check the presence of hypertension and infl uencing factor like overweight.High risk children who are overweight and obese should be given close follow-ups.Extended research is required to fi nd out association of hypertension and various risk factors like diet, regular exercise and weight reduction.Appropriate health education need to be given at home and school so that these risk factors can be eliminated in early stages itself.

Limitations
This was a cross-sectional study mainly intended to get blood pressure distribution and its relation to anthropometric measurements among school children, so to obtain a more precise idea about trends of blood pressure some longitudinal studies may be required.Further similar studies can be done with a larger sample size in this region to get more accurate results of blood pressure for children and adolescents.

Table 2 : Frequency distribution of SBP & DBP for adolescents in different age
International Journal of Medicine and Public Health | Oct-Dec 2014 | Vol 4 | Issue 4